Help with Synch AC Motor

Hey Bill,

A quick word of advice from having done something like this myself. Even if it's free, a 27.5 HP 220 Volt 3 phase motor running on single phase, which is what the RPC does, uses "heaps" of hydro! I had two sweet 25 HP freebies that I tried, but the currents were out of sight, so I bought used 7.5 to run 5HP and am well satisfied. Even if you don't mind the "cost" of operating the bigger ones, you may find that unless you have a 200 amp service available, you will be loading the total service pretty high.

I can't say for sure, but do what-ever it takes to determine that these are in fact motors, and not generators. The T1-1 and T1-2 don't mean much to me off-hand, unless they are for temperature sensing (which is critical in a generator), but the F1 and F2 sure sound like field leads as used in a generator. On the other hand, as a generator, the larger wires would more commonly be labeled A1, A2, so maybe I'm way off base here. When you say "smaller", what are the comparative sizes? Oh...they don't have brushes and/or a commutator do they?

Take care.

Brian Lawson, Bothwell, Ontario.

There are 2 7,5 hp motors. They are motors. they were used to cool and pump water for some electronics.

I have read that syncronouse needs a DC voltage to the rotor.

These units are pretty well sealed , I wouldnt want to try to take them apart.

Bill

I guess this is a Top Posting thread

The synchronous 3 phase motor might be a very interesting idler for a rotary phase converter. I remember Fitch saying that he'd like to test one. If I had two motors like yours, I'd ask Fitch if I could give him one. I sure would like to hear moreabout your synchronous idler project. If that was my motor, I'd try conducting some DC thru the little white wires and spinning the shaft to see what kind of voltage is at the (not connected) stator leads.

Jerry

Are they really synchronous motors? Do they have a set of slip rings associated with the smaller while wires?

Bob

They dont need slip rings to be synchronous if they are designed to excite the field with an "inside out" alternator, as you know.

Jerry

I looked at the second motor and it has an extra data plate . It says alternator 240 Volts 1 phase 3KVA cycles 2040

These motors are quite long for their diameter. About twice as long as a normal motor for the same diameter.

Can anyone tell me why the cycles are so high.

These motors have a water pump on one end and a fan and radiator on the other. I was told that they were used by the airforce for xray equipment. I can get another one or two of these motors free if I can find a use for them. IE rotory convertor, generator head etc. But I would like to know what I have.

Thanks for the help Bill

Ok, it's *not* a motor. It's an alternator, or an AC generator if you please.

If it was used as the power source for an X-ray tube, the high frequency would allow the designers to use a very light high voltage transformer between the alterator and the X-ray tube.

Probably nothing worth more than the scrap value.

I think that it has the two dataplates because it is a synchronous motor with the altenator on one end used as the exciter. The motor end is 60 cycle 3 phase.

Jerry Martes knows a lot about stuff like this. If he responds, I'd suggest paying attention.

equipment.

To me, it sounds like they are just small MG sets but with an alternator instead of a DC generator.....

Kinda like I was questioning earlier, about the leads the OP described. May be more of a Frequency Converter than a common MG set, which to me usually meant AC to DC, but doesn't HAVE to be I suppose. Although typical military is for 400Hz. And does the data-plate mean it is a DC ripple at 2400, which does describe an alternator.

Brian Lawson.